1. Field of the Invention
The present invention generally pertains to industrial fabric treatment machines and, more particularly, to access doors for industrial horizontal-axis fabric treatment machines.
2. Description of the Related Art
During the development of horizontal axis fabric treatment machines it has been common to provide a door in the cylindrical sidewall of a clothes treatment cylinder or drum to allow access into the interior of the drum for insertion of items therein and removal of items therefrom.
Typically, the door is formed by one or more curved plates of steel. The weight of the door combined with the weight of treated fabric thereon requires a rather massive support structure to maintain the door on the drum. The load on the door is primarily supported by the bending stiffness of the door. Bending stiffness describes a resistance to a combination of stresses that the door experiences, such as tensile, compressive, and shear stresses. Bending stiffness inefficiently supports the weight, and requires the door to be mechanically stronger than would be required if the membrane stiffness of the door could be exploited. Generally speaking, membrane stiffness is a resistance to a single type of stress, such as tensile stress, wherein all parts of the door are under tension and thereby cooperate to transfer the load to the surrounding drum.
Doors conventionally employed in fabric treatment machines are stiff and inflexible, and require mechanically strong hinges to mount the door to the drum. These hinges are expensive, and require the door to pivotally open about a fixed axis which, depending upon the orientation of the washing machine to the surrounding equipment, may not be convenient.
Therefore, there exists a need in the art for an access door for an inner drum of a fabric treatment machine which selectively pivots about one or more axes. Moreover, there exists a need in the art for a door which employs or exploits membrane stiffness to support the load of processed or treated fabrics, and thereby more efficiently supports the treated fabrics than doors which rely upon bending stiffness, as in the prior art. There also exists a need in the art for a door which eliminates the need for expensive hinges.